Petroleum well completion overview

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FOREWORD
This book, with named PETROLEUM WELL COMPLETION OVERVIEW is an
overview of Well Completion, with content general definition, equipment’s such
well Casing, Liner, Tubing Packers, and Christmas tree, also describe their
functions, design, and processes in common.
This book also describe generally about the process of running casing and
cement, perforating in under balance condition, production preparations,
stimulation treatments and sand control. stimulation treatments in this book
comprises matrix acidizing, hydraulic fracturing, and fracture acidizing. Sand
control comprises gravel packing, frac-packing, variant techniques.
Suggestions and constructive criticism is expected in the preparation of the next
book about Overview petroleum industry.
A. ANRIANSYAH

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TABLE OF CONTENTS
FOREWORD............................................................................................................................... ¡
TABLE OF CONTENTS.............................................................................................................. ¡¡
1. WELL COMPLETION DEFINITION....................................................................................... .1
2. WELL CASING …………………………………...………………………..…………………………1
2.1 Well Completion procedure..............................................................................................4
2.2 Well Casing Function ......................................................................................................8
2.3 Well Casing in Drilling Process .....................................................................................10
2.4 Liner ............................................................................................................................. 14
2.5 The Conductor Casing ................................................................................................. 15
2.6 Well Casing Component............................................................................................... 16
2.7 Well Casing Design ...................................................................................................... 17
2.7.1 Tension ................................................................................................................ 20
2.7.2 Collapse .............................................................................................................. 21
2.7.3 Burst stresses ...................................................................................................... 22
2.7.4 Corrosion ............................................................................................................. 23
3. RUNNING CASING AND CEMENT....................................................................................... 24
3.1 Accessory Equipment .................................................................................................. 25
3.1.1 Guide Shoe ......................................................................................................... 25
3.1.2 Float valve ........................................................................................................... 25
3.1.3 Scratchers ........................................................................................................... 27
3.1.4 Centralizers ......................................................................................................... 27
3.2 The Process of Running Cement.................................................................................. 28
4. PERFORATING ... ............................................................................................................... 32
5. TUBING ... ........................................................................................................................... 34
6. PACKERS ... ....................................................................................................................... 36
6.1 Packer Function.............................................................................................................36
6.2 Packers Configuration....................................................................................................37
6.3 Permanent Packers........................................................................................................40
6.4 Temporary Packers........................................................................................................41
7. CHRISTMAS TREE ... ......................................................................................................... 42
7.1 Christmas Tree Function..............................................................................................43
8. PERFORATING IN UNDER BALANCE CONDITION............................................................45
8.1 Running Perforating wireline..........................................................................................47
9. PRODUCTION PREPARATIONS...........................................................................................50
10. STIMULATION TREATMENTS ...........................................................................................51
10.1 Stimulation Function ....................................................................................................52
10.2 Matrix Acidizing ...........................................................................................................56
10.3 Hydraulic fracturing .....................................................................................................57
10.4 Fracture Acidizing .......................................................................................................60
11. SAND CONTROL………………………………….…………………………………………….…62
11.1 Gravel packing…………………………………………………………………………….…62
11.2 Frac-Packing…………………………………………..……………………………….……63
11.3 Variant Techniques…………..……………………………………………………..………64
12. CONCLUSION ................................................................................................................... 66
REFERENCES .......................................................................................................................... 67

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1. WELL COMPLETION DEFINITION
Well completion means preparing the well for production, of course
well completion is worded only when the well have sufficient amount of oil and
gas to be commercially viable. That is why data from all the evaluations and tests
is so important.
Now with probable positive evaluations, we are ready to complete the
open hole, part of the well. These open holes, where we conducted our wire line
tests and coring can now be cased and cemented to become a closed Cased
Hole. When we talk about running casing in well completion, we are only
referring to the casing the zone or zones of interest in the open hole. These
casing strings are referred to as production casing it is sometimes easy to
confuse the function of production casing, with those of surface intermediate
casing (Pic. 01)
Pic. 01. Well Completion - Well Casing
2. WELL CASING
It can be explained that surface casing for example is the first casing
string to be run when the well is first drill, as the name imply the surface casing,
since it's the top part of the well and his attached to the well head, it's primary

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function is to protect the groundwater formations from contamination (Pic. 02). In
deeper well a second type called an intermediate casing is running and
cemented, intermediate casing is required, its primary function is to protect and
support the hole above the zone or zones of interest (Pic. 03). Surface casing
and if needed intermediate casing strings are install during drilling on all wells
regardless of whether they are commercially viable or not. The production
casing strings on the other hand are only run when the well shows problems of
becoming a producing oil well, running and cementing this casing segment are
part of the first steps in well completion (Pic. 04).
Pic. 02. Well Casing – Surface Casing Function

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Pic. 03 Well Casing – Intermediate Function
Pic. 04. Well casing - Production Casing Function
Once the production casing is run, cemented and attached to the surface,
and the intermediate casing string at the wellhead, these casing form what is
known as a close hole or cased hole (Pic. 05). This hole from the top to the
bottom is now sealed off from the natural fluids and solids that exist in the sub
surface (Pic.06).

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Pic.05. Well completion – Open Hole
Pic. 06. Well completion – Cased Hole
2.1. Well Completion Procedure
Well completion however, involves more than running casing and sealing the
hole, to complete a well after the casing running and cemented, the following
procedures can be performed:

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1. Perforation
Once the production casing in place in the zones of interest, the casing then
perforated (Pic. 07), which means blast through the casing and the cement deep
into the formation.
2. Stimulation
After perforating the zone is stimulated (Pic. 08), so that inadequate
production or flow rate of the hydrocarbons can be attained.
3. Gravel packed
If its needed the zone can also be gravel packed (Pic. 09) to stop sand
production
4. Tubing, packers, and a christmas tree
Finally the well is equipped with tubing, packers and a christmas tree to
control the flow of fluids to the surface (Pic. 10).
Pic. 07. Well completion – Perforation

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Pic. 08. Well completion – Stimulation
Pic. 09. Well completion – Gravel Packed

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Pic. 10. Well completion – Tubing, Packers, X-mas tree
Before we described each of the above procedures, to finalize well
completion in more detail, we take a minute to explain one action is taken when
are well is not commercially viable. When a well stated no zones of interest or
has a little commercial viability it is declared a dry hole. This well would be
permanently plug, then abandoned call P&A (Pic. 11), for plugged in and
abandoned, this procedure requires that several cement plugs be placed in the
hole to seal it.
Pic. 11. Well completion – Plug & Abandoned (P&A)

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As we know that wildcat wells, wells in areas where no one has drill before
are more likely to be dry holes. The industry figures suggest that as many as
seventy five percent (75%) of all drilled wildcat wells are dry. P&A procedures
therefore, can become quite routine in wildcat areas, in this book then would
pertain to the procedures and their functions used in well completion. Although
already mentioned well again present the three types of casing string and explain
their functions, in addition we illustrate the different procedures and the specific
equipment needed to ready the well for production.
Specifically we present a brief summary of casing design, casing
equipment, cement operation, Perforation, well stimulation, sand control along
with the file equipment needed to prepare a well for production (Pic. 12).
Pic.12 Well completion – summary
2.2. Well Casing Function
Let’s start with the four main functions of the surface, intermediate, and
production casing strings with their cement sheet or covers (Pic. 13). First, all
three of the different types of casing protect the whole from the mud, that's
preventing soft formations of shale from growing water out of the mud which then
can cause the shale to swell and blocked or impede the drilling operations.

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Pic.13. Well Casing Function
In addition casings prevent surface sediments and other unconsolidated
formations from being eroded by the mud system. Second function relates all to
surface casing, this casing protect near surface freshwater zones from
contamination by deeper salt water zones. we sure people rely on these
freshwater aquifer, polluting these aquifer is usually prohibited by law or can
create serious environmental issues. Third all three types of casing the surface,
the intermediate, and the production casing provide a smooth entryway and path
for running tools in and out of the hole. Finally in production casing, its
surroundings cement sheet isolates down the hole zones, so that the different
zones can more easily be produce separately.

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Now let's examined the standard procedures involve the closing and open
hole. The first step in closing and open hole is to drive the production casing
string to the bottom of the hole. The casing string is permanently set in the well
by pouring concrete into the annular space between the casing and the wall or
the hole. let me point out here, that because the drilling string must be able to
fish comfortably inside the casing string, the casing string pipe must be large
enough to allow the drilling string pipe fit inside it (Pic. 14). Like the drilling string,
the three types of casing strings consist the multiple joints but of larger diameter
pipe that is screwed together one join out of time as it is inserted to the bottom of
the hole at total depth (TD).
Pic. 14. Well Casing for Closing Open Hole
2.3. Well Casing in Drilling Process
Casing strings are run and cemented into place as the well as drilled
deeper to protect the hole from further exposure to the circulating mud. The exact
number of strings depends on the depth of the well, the relative stability of the
formation penetrated, and the characteristic of the drilling mud (Pic.15). As

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discussed earlier, as each casing string is run it is run inside the previous string
that was slightly larger. Conversely the diameter of each new string will be
smaller than the one it fits into as the casing is run deeper. Imagine those sets of
plastic balls that you can buy at any supermarket where the smaller bowl fits
inside a larger one which fits inside and even larger one until you get to the
biggest bowl with all the small bowl fitted neatly inside. there for, to be sure that
the casing string fits together properly, it is imperative that the casing program
preplanned before drilling begin so that the surface hole and pipe can be large
enough to accommodate all the strings that will be push through it. Keep in mind
that the final string must be small enough to fit through all casing joints while still
being large enough to allow oil or gas to flow adequately for its capacity.
Pic. 15. Number of Drilling & Casing String
When inserting the initial casing string, the drilling operation, drills their
large diameter surface hole to unconsolidated surface material and protects
sources of fresh water in the nearby water table, called the surface casing string.
It is usually a few hundred feet and runs to the bottom of the whole at the
beginning when drilling first begin (Pic. 16).

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Pic. 16. Surface Casing
Once in place cement slurry is then pump down the inside of the pipe and
circulated up the backside annular space between the casing and hole (Pic. 17).
Pic. 17. Running Surface Casing
Once the surface casing is in place, drilling resumed for shallow wells the
surface casing maybe all that is required before initializing the production casing.
For deeper wells or where the formation becomes unstable because of long
contact with the mud and intermediate casing string maybe necessary.

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A very deep hole may require two or three intermediate strings. To establish and
intermediate casing the surface casing must be drilled through using it smaller bit
that fits inside the surface casing pipe. The drillable shoe on the surface string
and the cement in the bottom of the hole is easily penetrated. Once the slopping
zone is penetrated the drill strings is pull and intermediate casing string is run to
the existing bottom and then cemented into place.
When using an intermediate casing it is important that this cement rises
high enough in the annulus to reach and tie into the cement in the surface casing
pipe. It is essential to provide an unbroken cement sheet that covers the entire
length of the hole, these steps or repeated as each success of string of the
intermediate casing is hung from the wellhead at the surface. Finally the
wellhead access is sealed, to seal off the annulus at the end of the casing string,
both the surface and intermediate of casing strings are installed while drilling
continues to total depth.
Once in the zone of interest that has been identified, it is not cased yet,
this section of the well is referred to as open hole. Basically it is the length of the
hole from the surface or intermediate casing strings to TD, as we know about
open hole, that open hole well logs and identify the lithology, measure
permeability porosity, the reservoir thickness, and fluid saturation are finalized
(Pic.18). Once the potentially commercial viable well is confirmed, this section of
the hole is then cased and completed (Pic. 19).
Pic. 18. Open Hole Logging

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Pic. 19. Cased and Perforated
Then the production casing, long string or oil string, the string is set
through the producing zone, and cemented, ensuring that it is tied to the string
above so that there is a continuous sheet of pipe and cement from bottom to top.
Later this casing and cement will be perforated to get access to the producing
zone.
2.4. Liner
In the zone that do not perforated well, a liner maybe run. Unlike casing
string, liners do not extend all the way to the surface, but are hung from the long
string as this illustration (Pic. 20). Liners although cheaper may a peer more
convenient but in fact are not preferred because they can cause difficulty in
running tools pass the restriction of the liner hanger. They also can limit the
control of water when production began.

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Pic. 20. Liner Casing
2.5. The conductor casing
A complete casing strings are preferred if conditions permit. Offshore is
different than onshore because of the need to run type through the water before
reaching the bottom of the ocean. When bottom supported units are used like in
an offshore platform and additional large diameter string, called a conductor
casing is then first run. The conductor casing is hammer into the sea floor and
then extended up through the water to the surface just below the rig floor (Pic.
21). This casing becomes a conduit or passageway for dill pipe and the mud.
With floating units like drill ships or a semi-submersible (Pic. 22), a guide
structure is fast and to the bottom of the body of water and secured through the
ocean for with piles. The blow up preventer are then latched into the guide
structure on the sea floor and then connected to the surface the a marine riser.
These riser these as function as conductor strings

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Pic. 21.Conductor Casing - offshore
Pic. 22. Offshore – Drill ship or Semi-Submercible
2.6. Well Casing Component
As you can imagine, casing and its different components can be very
expensive, so choosing the correct equipment for the depth and pressure of the

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well that is very important, and is usually up to the drilling team to calculate the
list expense casing that is capable of safely and adequately (Pic. 23).
Pic. 23. Choosing well casing Component
2.7. Well Casing Design
In casing a well so fluid can flow freely while containing the pressure that
could lead to danger his blow providing a margin of safety to protect the
monetary investment, the crew and the environment casing designs can be
critical especially in deep high pressure well (Pic. 24).

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Pic. 24. Casing Design consideration
The well thickness and yield strengths of each string of pipe must be
carefully planned to fit the conditions of the well (Pic.25). For example if the
casing pipe is too thin the casing can fail causing a blowout, in the other hand if
the casing is to thick than money you spent unnecessarily (Pic.26).
Pic. 25. Well thickness and yield strengths

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Pic. 26. Casing Design consideration consequences
Fortunately there are computers programs that helped simplify this
process to ensure adequate and safe design, there are four design criteria that
the drilling engineer must factor into his equations for the casing design (Pic.27).

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Pic. 27. Well Casing Design factors
2.7.1. Tension
The first is tension, since all the casing hangs from the top joined that join
must be strong enough to support all the strings, it is sometimes better to
strengthen the upper part of the string by using a thicker or high grade pipe, of
course if a thick wall is used the engineers must account for this way in his
calculations for the rest of the strings (Pic. 28).

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Pic. 28. Casing Design - Tension
2.7.2. Collapse
The next is the danger of collapse, this danger is where the cement has
just been circulated up the outside of the casing because the cement as much
heavier than the mud that is inside. The deeper the hole the greater the outside
in pressure differential is, strengthening for collapses usually done at the bottom
of the hole with a higher grade of casing (Pic. 29).

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Pic. 29. Casing Design – Collapse
2.7.3. Burst stresses
Third a burst stresses, like collapse, these tresses or concentrated at the
bottom of the a critical time for burst stress is an pumping up operation at the
beginning of the cement job and during a fracture treatment or stimulation
(Pic.30). The entire string is designed to be stronger at the top tension and at the
bottom for collapse and burst. The weaker casing pipe is usually in the middle of
the string.

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Pic. 30. Casing Design – burst stresses
2.7.4. Corrosion
The fourth is corrosion, in deep wells higher grade pipe must be used to
get the necessary strength because too thick walled pipe can be too heavy for
the tension (Pic. 31).
Pic. 31. Casing Design – corrosion

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Higher grade pipe however, is more susceptible to corrosion. For
example, the presence of hydrogen sulfide (H2S) is particularly troublesome,
because H2S can penetrate high strength steel to become brittle and lead to
cracks and breaks. In very deep high pressure sour gas wells nickel alloy pipe is
often the only solution, because it is very expensive, it is used only one nothing
else will do the job (Pic. 32).
Pic. 32. Higher grade pipe
3. RUNNING CASING AND CEMENT
Now let's turn our attention once again to the wellbore, in running
casing and cement the initial cementing called primary cementing creates a
sheet or cover of hard cement that fills the annulus space between the outside of
casing and the well board wall. as i mentioned earlier it's primary function is to
block fluid movement and pressure transmission up or down and the annulus,
subsequent cementing is called squeeze cementing, and it’s done to repair the
primary cementing or in connection with a work over a well that is being rework
because of declining production.

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3.1. Accessory equipment
3.1.1. Guide shoe
Let we describe the various pieces of accessory equipment needed when
running casing, then later cementing. In the illustration (Pic.33), you can view the
typical equipment set up, at the bottom is a guide shoe it has a rounded base
that run to the casing string in the hole to prevent the casing from sticking on
lodges, it can easily be drilled through later if necessary.
Pic. 33. Accessory equipment
3.1.2. Float valve
Next is the float valve, it can set either in a shoe called the floats shoe or
in a float collar located a joint or two above the shoe. The function of the float
valve is to prevent mud from filling the pipe, it also provides buoyancy to the pipe
which than lessons the load derek and the top joined of the pipe, as the casing is
run in the hole, the casing pipe is periodically filled with water at the surface to
reduce differential pressure that might cause the casing to collapse (Pic. 34).

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Pic. 34. Accessory equipment – Float valve
Inside the float valve, the ball and sheet type valve keeps the pipe close
while the casing is being run and opens it while the cement is being pumped in.
The valve and seat ball also prevents back flow of the fluid or the cement into the
drill pipe (Pic. 35).
Pic. 35 Accessory equipment - The valve and seat ball

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3.1.3. Scratchers
Next are the scratchers or wall cleaners they removed mud cake from the
sides of the hole, attached to the outside of the pipe these scratchers allow the
pipe to make better contact with the size of the hole as the cement is pumped
into the annulus (Pic. 36). As you might guess, smoother walls along the sides of
the open hole allow a better seal to form between the cement and the formation
rock. Radial type scratchers required that the pipe reciprocated for moved in and
up and down motion before and during cementing. Vertically amounted
scratchers required the pipe to be rotated.
Pic. 36. Accessory equipment – scratchers
3.1.4. Centralizers
Centralizers set at the top of selected joints, they are attached to the
outside of the casing pipe to center the pipe in the hole in preparation for
cementing (Pic.37). Centralization of the pipe is essential because for maximum
functionality the cement sheaf must evenly and completely surround the pipe.
These are the essential pieces of equipment used in preparation for cementing.

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Pic. 37. Accessory equipment - Centralizers
3.2. The Process Of Running Cement
Let we now described the process of running cement, first dry cement is
mixed with additives made up of accelerators, retarders, and density adjusters
(Pic. 38). The function of these additives is to adjust the dry cement properties to
fit the conditions of the well, accelerator speed up the setting time of the cement
(Pic. 39), retarders to the opposite they prevent premature setting in deep high
temperature well (Pic. 40). Density adjusters increase the cement weight to
reduce pumping pressures or to permit a higher cement column without
fracturing the formation (Pic. 41).

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Pic. 38. Cementing – Accelerators, retarders, & density adjusters
Pic. 39. Cementing - Accelerators

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Pic. 40. Cementing - Retarders
Pic. 41. Cementing - density adjusters
After the casing in place, the cement is properly blended with water and
the hole does prepared for pumping, first a hard rubber rupture plug is inserted
into the casing followed by the cement slury, this plug will separate existing mud
from the new cement (Pic. 42). Pumps to the bottom of the hole the cement slury
pushing the plug in front as it flows down forces the rupture plug into the seat in
the float collar. Once in place the driller slightly increases the well pressure to
break through this rupture plug. Once the plugs broken the cement slurry
displaces the existing mud in the annulus, when adequate cement has been
pumped a second plug called seal plug is then inserted. This seal plug serves the
separate the cement slurry from the fresh mud that follows. Finally the cement

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slurry is displaced out of the casing into the annulus. The cement job was
completed when the second plug the seal plug land in seats in the grooves in the
floats valve, this landing is signal at the surface by a sharp pressure increase.
The pumps are then shut down which allows the pressure to drop.
Pic. 42. Cementing process
The decreasing pressure causes the flow valve to close preventing the
heavier cement in the annulus from running back into the casing. After the pumps
or shut down well operations or suspended for from twelve to twenty four (12-24)
hours, so the cement can set (Pic. 43).

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Pic. 43. Cement Slury set 12-24 hrs
4. PERFORATING
With the cemented casing in place the next task is to perforate the
casing in the zone of interest, called the pay zone. Perforating mean blasting
through the walls of the casing, the cement sheets and continuing on for about
one (1) meter into the formation rock, it is through these holes that hydrocarbon
fluids will pass to the surface when production begins (Pic. 44). To blast through
the casing and cement jet perforator are set to 4-8 holes per foot, each shot is
rotated ninety (90) degrees or one hundred eighty (180) degrees from the one
above throughout the pay zone, to blast these jet perforators through the casing
and into the formation, casing guns are used. The retrievable and reusable these
casing guns are made of strong wing constructed steel which are run with an
electric wireline (Pic. 45).

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Pic. 44. Perforating Process
Pic. 45. Jet perforators Casing Guns
Before first firing, the gun and the hole is filled with salt water. This salt
water is called water blanket or load brine, when the well has perforated the
water rush out through the new perforations killing the well and preventing a blow

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up. With the potential for further damaging the formation near the wellbore using
over balance conditions the engineering team made decided to stop for the
perforations until the world has been prepared for production. This means that
the well will be outfitted with tubing packers and the christmas tree there
accommodate perforating in underbalanced conditions. In addition many of the
subsequent well treatment processes described, then the next segment of this
book are optimally done after the well has been outfitted with these three
components, they include the wellhead and the various processes of preparing a
well for production and will be discussed here. In preparing the well for
production smaller diameter pipe, called tubing is installed down the casing with
a packers at the bottom (Pic. 46). Let we point out here that the permanent
casing is rarely used as a conduit to get oil and gas to the surface. Remember it's
main function along with the annulus is to seal the wellbore and keep it sealed.
Pic. 46. Tubing, Packers, & Wellhead
5. TUBING
Instead smaller tubing installed through the casing is used to bring the
fluids to the surface. Manufactured in joints a thirty (30) feet with threaded
couplings the diameter of tubing can vary, depending the fluid amount projected
to be produce (Pic. 47). For example small tubing that is to and three eight

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inches 2 3/8” outside diameter is used for shallow low productivity wells. While
large six inch 6” outside diameter tubing is used in high volume gas well.
Pic. 47. Tubing size
In any case tubing is smaller than either the drilling casing pipe and is
relatively lightweight when compared to them, because of two the smaller size
and weight it can be run in and out of the hole by work over rig out fit with small
or a hoisting equipment when you would find any drilling rig.
Here you can see that these strings hang from the tubing hanger in the
wellhead and irretrievable unlike the permanent casing strings. Keep in mind also
that although only one set of casing is ever run tubing because of its smaller size
can be run through the casing and single, dual or multiple strings (Pic. 48).

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Pic. 48. Tubing String – Single, dual, & multiple
6. PACKER
6.1. Packer Function
Inside the tubing, the packer is inserted, and then used to seal off the
tubing from the casing, by sealing off the tubing from the casing, the more easily
replaceable tubing protects, the more permanent casing from the pressure and
corrosive elements found and the crude oil gas as they pass to the surface,
Packer protect casing from pressure and corrosive elements in the oil and gas
(Pic. 49).
Pic. 49. The packer

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The dual configuration is preferred on production from the well comes
from two different zones that the engineering team wants to keep separate, in
addition dual or multiple strings offer economic incentives we're warranted
because only one well has to be drilled instead of multiple ones. Both dual and
multiple strings can be installed but multiple strings are less popular because of
their mechanical complexity.
6.2. Packer Configuration
Packers come in many configurations and have many functions (Pic. 50),
but basically they have three things in common. First each packer is made of a
flexible rubber sealing element that closes off the space between the outside of
the tubing and the inside of the casing (Pic. 51). Second they all have
mechanical projections that dig in to the casing to keep the packers solidly in
place (Pic. 52). Third they all have one or more holes for vertical penetrations
which permits single dual or multiple strings of tubing to pass through the packer
(Pic. 53).
Pic. 50. Packers Configuration

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Pic. 51. Made from flexible rubber sealing element
Pic. 52. mechanical projections

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Pic. 53. have one or more holes
Depending on requirements of the well, two (2) different types of packers
called a permanent and retrievable or temporary packer are available (Pic. 54).

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Pic. 54. Packer type; Permanent & Temporary packer
6.3. Permanent packers
Permanent packers are run into the wellbor on tubing or a wireline and set
with a small explosive charge, when this charged these explosive charges
generate a large pressure that it allows the packer to expand and then we firmly
and permanently set into the size of the casing. once it set the tubing strings then
run through the packer the rubber sealing elements on the outside of the packer
seal against the smooth inside of the packer, these permanent packers cannot
be retrieve but constructed of materials that can be drilled through easily (Pic.
55).

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Pic. 55. Permanent packers
6.4. Temporary packers
Screwed directly into the production tubing string retrievable or temporary
packers are firmly, but temporarily set by rotating picking up setting down or
pressurizing of the tubing, designed to be fully retrievable these retrievable or
temporary packers are used (Pic. 56), for example, when a secondary cementing
job or squeeze job is performed. Now as we mentioned earlier a squeeze job is
when additional cementing is required after the additional cementing has taken
place or when work over is in progress. During the process of preparing a well for
production, the surface casing is mounted on the wellhead. It function is to seal
off the annular spaces between the strings each additional casing string and
tubing string are hung from the well head as they are run.

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Pic. 56. retrievable or temporary packers
7. CHRISTMAS TREE
Once the well as completed however, access to the wellhead is no
longer required so they are usually place just below ground level (Pic. 57).
Pic. 57. Christmas Tree

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Finally a Christmas tree is installed, containing valve manifold that controls
flow in the tubing, they must be strongly constructed to contain full of reservoir
pressure, a christmas tree function is to control the pressure. In the illustration
(Pic. 58), the main valves that control the well pressure or labeled, they are
choke, master valve, crown valve, the wing valve, and the safety wing valve.
Pic. 58 Christmas tree function
7.1. Christmas tree function
Let discuss the function of each. We start with dual master valves which
are used to shut in the well, the top valve controls the well pressure, the bottom
valve acts as a backup. Usually it kept open the bottom valve can be used in the
event if the first valve fails for whatever reason. Next the crown valve or lubricator
valve is used when the lubricator is attached, it is used when well service tool
operations are being conducted such as through tubing perforations (Pic. 59).
We will discuss more about through tubing perforations in the next section when
we talk about perforating in under balance conditions.

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Pic. 59. Crown valve
The wing valve is normally used for the routine opening and closing of the
well, the choke is an orifice that very since sized to control the wells flow rate, it
also confined full well pressure to the tree that's protecting equipment down
string. Finally the safety valve automatically shuts in the well when unsafe
conditions are recorded such as excessively high or low down string pressures
(Pic.60).
With the well prepared for production, we can now return to finalize any
addition treatment that is needed before actual production begins. As we know
before the perforating in over balance conditions, high lighting the damage to the
vicinity around the wellbore that it can cause, we mentioned that the engineering
team may prefer to perforate in another way. If they like to perforate in under
balance conditions the well has to be made ready with tubing, packers and a
christmas tree to control the pressure required for under balance perforating.

45
Pic. 60. Wing valve, Safety wing valve, and Choke
8. PERFORATING IN UNDER BALANCE CONDITIONS
Since we have now explained the components used to prepare a well
for production, we can now proceed with explaining how the well is perforated in
under balance conditions. Perforating in under balance conditions is considered
best practices (Pic. 61). In under balance perforating, wireline through tubing
perforating with the small diameter gun that can fit through the existing tubing is
preformed after the well has been prepared for production, as the packers,
tubing, and surface valve called the christmas tree.
With the packers and christmas tree in place, the fluid level in the casing
can then be kept lower so that the hydrostatic pressure is less than the formation
pressure (Pic. 62). In addition once the zone has been perforated in under
balance conditions, it can then be immediately placed on production, not only
saving time and money through tubing perforating can also greatly reduce any
formation damage that might be, because when the flow rates are stopped
known as killing a well to run down a hole equipment (Pic. 63).

46
Pic. 61. Perforating in Under balance Condition
Pic. 62. Hydrostatic Casing is kept lower than the Formation Pressure

47
Pic. 63 Tubing perforating can saveing time & money, reducing Formation damage
8.1. Running Perforating Wireline
In running wireline through tubing perforating the crown valve in the
lubricator on a tree is opened. The perforating gun is then run into the well in
fired; the stuffing box sitting at the top the entire lubricator holds the pressure
build up in the formation to prevent blowouts. This pressure build up in the
formation cause of the formation fluids to rush out into the wellbor, flushing out
the jet charge debris along with the damage formation rock under balance
perforation, in other words immediately cleans up around the area impacted by
the perforating which should then enhance flow rates when production begins.
When the gun is pulled back into the lubricator, the lubricator valve on the tree is
closed. The pressure then blood off the lubricator and the gun is removed. The
wing valve is opened in the christmas tree and the oil should begin to flow (Pic.
64).

48
Pic. 64. Running Perforating wireline
Another typed tubing conveyed perforating also permits under balance
perforating in a fully equipped well (Pic.65), tubing conveyed perforating guns are
run into the hole below packer on the bottom producing string, as you can see
tubing conveyed perforating guns are much longer with larger charges. The
advantages tubing conveyed perforating allows the perforating gun to be pushed
into highly deviated or horizontal holes that would be inaccessible to wireline
conveyed gun (Pic. 66).

49
Pic. 65. Wireline through tubing perforating
Pic .66. Wireline tubing conveyed perforating

50
9. PRODUCTION PREPARATION
After perforation conducted, then the well is prepared for production
with casing, cementing, perforations, tubing, packers, and a christmas tree all
attached to the well head (Pic.67), it may be assume that the well reservoir fluids
will begin to flow freely into the wellbor and up into the stock tank. In wells with
highly permeable formations, this is permeable well that flow easily without
further procedures have, called natural completions (Pic.68).
Pic. 67. All equipment attached to the well head

51
Pic. 68. Natural Completion
10.STIMULATION TREATMENT
Many wells however require what is known as stimulation treatment,
used because it provides the reservoir fluid better access to the wellbore,
stimulation treatment helps allow the fluid to flow in formation with lower
permeability, by pumping acid into the formation or by creating hydraulic
fracturing, and stimulating treatments can be highly effective. It can cause
production rates to double, triple, or even quadruple. This increase in production
can turn a non-viable commercial well into a viable one. Surprisingly in the fluids
journey from the perimeters of the reservoir through the stop tank, it is the last
few inches of reservoir rock where the obstacle is encountered. The stimulation
treating operations are used in areas with low permeability. High permeability
zones with natural completion do not usually needs stimulation (Pic. 69).

52
Pic. 69. Stimulation Treatment
10.1.Stimulation function
Let we see an illustration (Pic. 70) that helps explain the function of
stimulation, here you see the geometry of radial flow, as the flow oil approach the
wellbore, the flow arrows begin to crowd each other out. The fluid represented by
these flow arrows becomes constricted as it approaches the wellbore. This
construction reduces the flow resulting in a decreasing the fluid volume that
reaches the wellbor, more evidence in lower permeability formations than in
higher ones this reduction in the fluid volume can resulting lower fluid flow when
production begins (Pic. 71). In addition to this natural restriction just described
there may also be formation damaged which may be also preventing the fluid
from flowing freely. Because when the formation rock comes into contact with the
drilling mud, formation damage can appear as one of two types. First, some
formations containing clays absorb mud filtrate rate and expand, this expansion
may hamper or plug the formations permeability. Second, solids in the mud can
become trapped in the pores of the formation also reducing permeability (Pic.
72). Working in tandem or an isolation natural restriction and formation damage
can create unwanted bottlenecks in the immediate vicinity of the wellbore that
can greatly impact the wells production rate (Pic. 73).

53
Pic. 70. Stimulation Function
Pic. 71.Lower fluid flow when production begin in low permeability

54
Pic. 72. Natural restriction

55
Pic. 73. Formation damage
Production rate is figured by calculating the number of barrels per day by
a well or wells can produce, one of the most important factors and calculating this
number is estimating how fast the reservoir can reproduced, not just estimating
how big the reservoir is. Therefore successful stimulation treatment to eliminate
or reduce the impact of these bottlenecks can better ensure the profitability of a
well. let's look at some stimulation treatment operations, they are matrix
acidizing, hydraulic fracturing, and fracturing acidizing (Pic. 74).

56
Pic. 74. Stimulation treatment operations
In all stimulation operations, treating liquids are pump out of the surface
tank, down the well, inside the tubing anchored by a packer out to the perforation
and into the formation. In hydraulic fracturing and fracture acidizing, along with
these treating liquids several thousand pounds of surface pressure are also
introduced into the formation. In any event, the specific type of treating liquids
coupled with pressure is determined by the formation rock and it's permeability in
the pays zone.
10.2. Matrix acidizing
The primary function stimulation is to remove formation damage so that
the permeability of the near well bore formation is improved. For example in
matrix acidizing, different kinds of acids depending on the formation rock type are
used to increase the number of fractures. Hydrofluoric acid is used in sandstone
reservoir while hydrochloric acid better result in limestone reservoirs (Pic. 75).
Regardless of the acid used the appropriate acid slowly pump down the wellbore
and out through the matrix of the reservoir, while taking care and make sure that
no additional pressure is exerted on the reservoir rock, which might cause the
formation to fracture in one productive ways.

57
Pic. 75. Type of acid for different rocks
10.3. Hydraulic fracturing
The second type of stimulation treatment is hydraulic fracturing. Hydraulic
fracturing is the most effective stimulation treatment for the type sandstone
formations, usually found on older more consolidated continental sediments.
When using this treatment, pump on the surface create several thousand pounds
of surface pressure that are then channel into the wellbore. To break down the
formation in controlled fractures, in addition water that has been mixed with gel
and chemicals to increase its viscosity is pumped into the well to help the
fracturing process. In combination with a down hole, increased pressure from the
pressure pumps at the surface, this gelled water enabled to increase sandstone
pressure to be evenly distributed across the pay zone, that's enabling further
fracturing for hundreds of feet in more or less horizontal direction. To limit leak off
or run off into the surrounding formation polymers or added to the gelled water
(Pic. 76).

58
Pic. 76. Hydraulic fracturing
In addition, gel in the water makes the water slippery enough to reduce
friction (Pic. 77), that lowering pumping horsepower requirements (Pic. 78). Once
the fracture is extended far enough, a propping agent often large rounded sand
grain is introduced into gelled fluid being pumped.
Because of the high viscosity of the gelled water, the propping agent is
suspended evenly throughout the solution as it is pump out into the fractures.
When the gelled water with propping agent reaches the formation the propient for
seeps and then packs into the cracks in the formation. When the formation is
saturated pumping as then stopped. As the pressure goes down the fracture,
now with the artificially in those pressure remove and returned it's a normal
pressure condition tries to close but is instead held opened by the propient
(Pic.79). These fractures, now filled with well sorted large propane particles form
an excellent flow path for the oil and gas.

59
Pic. 77. Gel in water makes the water slippery
Pic. 78. Lowering pumping

60
Pic. 79. Propane particles
10.4. Fracture acidizing
The last stimulation treatment is a combination of matrix acidizing and
hydraulic fracturing, called fracture acidizing, it is used to stimulate production in
limestone and dolomite reservoir. Because limestone and dolomite composed
largely of calcium carbonate, they will dissolve in hydrochloric acid (Pic. 80). In
this operations HCL injected at high enough pressure in order to fracture the
formation and through vertical direction, as the pressure of the pumped acid
extends the fractures, it chemically edges or dissolves and irregular surface on
the sides of that fracture which losing high volume flow channel through the
wellbore. Like in hydraulic fracturing, the fractures with normal pressures
returning, trying to close when the pumps are turned off, but these edge high
volume flow channels remains open (Pic. 81).

61
Pic. 80. Fracture acidizing
Pic. 81. Propping agents kept fractures open
As we know this fracture changes the flow pattern around the wellbore
from radial flow to a much higher volume lateral flow pattern.

62
11.SAND CONTROL
11.1 Gravel packing
Before production begins, for some wells and additional procedure called
gravel packing maybe wanted, and for example in sandstone reservoir consisting
largely of unconsolidated sand grains with very little cementation is usually
pushed to the surface along with the oil and gas. When produce with high
velocity oil and gas streams, it can erode any steel that might come in contact
with these grains, the sand entering the wellbore act like a little bullets blasting
into the casing or tubing most metallic surfaces it comes in contact with. The
continued blast of these grains of sand can cause the casing dissplit or can cut
through the tubing. Gravel packing used to control the sand from being produced
with the well. Even though gravel packing is expensive and is not completely
successful in many wells it is never the less attempted on virtually every
completion and sand producing areas (Pic. 82).
Pic. 82. Gravel packing
Let’s look at the process and the steps involved in gravel packing, first a
wire wrap screen is run into the hole on tubing with a specialized packer called
across over packer, unlike other packers to crossover packer allows the fluids to
crossover from the tubing to the annulus and back again (Pic. 83). Next the
gravel is mixed with gelled water and then pump down to tubing through the
crossover passage in the packer into the annulus space on the other side of the
screen. As you can see the gelled water passes through the interior of the screen
crosses over in the packer into the annulus and circulates to the surface,
because this large graded sand gravel is larger than the mesh in the wire wrap
screen, it is filtered out by the screen trapped the gravel dropped to the bottom
and accumulates in the annulus (Pic .84). Finally at the gravel working as barrier

63
or filters out the sand trapping it in the gravel pack and stopping it from flowing
into and through the wire screen.
Pic. 83. the process and the steps involved in gravel packing
Pic. 84. graded sand gravel in wire wrapped screen
11.2 Frac- packing
Another approach to controlling sand is called Frac- packing used in more
tightly consolidate formations it's blend gravel packing techniques with hydraulic

64
fracturing techniques (Pic. 85). Using this method the packing fluid is injected at
a rate high enough to build up pressure and fracture the formation. Pumping
continues as the gravel is packed into the formation, just like in gravel packing its
function is to stop the grains of sand from flowing into the wellbore (Pic. 86).
Pic. 85. Frac-packing with Hydraulic Fracturing techniques
Pic. 86. Frac-packing function
11.3. Variant techniques
Even with sand gravel procedures, sand can still managed to as the
wellbore, to protect against the eventual sand accumulation. Once production

65
has commenced in these formations the engineering team uses variant
techniques. The first is to installed blast joints constructed with extra thick walls,
in addition we may use hard rubber coatings on the outside that can help the
tubing withstand the sands of eroding actions (Pic. 87).
Pic. 87. Variant techniques in Sand Control
Another method is used in areas where the oil and gas loss stream,
changes direction in this scenario these continual motion changes, can cause the
valve manifold on the christmas tree at the surface to cut out at its elbow fitting. A
failure of this fitting can cause a dangerous blow up, where the possibility of sand
accumulation is continual problem, the tubing and surface equipment must be
cleaned regularly. For example, when sand settles out of the oil and gas and
bridges over the wells tubing, it can completely plug off production (Pic. 88). To
deal with this accumulation, it may be necessary to work over the well to wash
out this accumulated sand. Finally accumulated sand can also drop out of
suspension at the surface and accumulate in surface equipment such as
separator. Regular maintenance can help keep most surface equipment working
properly. As we can see sand production and accumulation from these on
cemented unconsolidated sandstone formations require constant monitoring with
periodic clean out.

66
Pic. 88. Workover to washout accumulated sand
12.CONCLUSION
After having spent a lot of time and money on the well, then
complete. We have run the casing, we have cemented the casing, perforated the
zone of interest, installed the christmas tree, tubing, and packers for the low
permeability zones, with stimulated the well with acid, we have done sand control
with gravel packing, etc. Next we are going to perform Field Appraisal &
Development, and the Artificial Hydrocarbon lifting.

67
REFERENCES
 Agip, Well completion and work over course, Agip, 2v., 1996.
 Economides M.J. et al., Petroleum well construction, Chichester-New York, John
Wiley, 1998.
 Lau Richard, Overview of the Oil Industry – Well Completion, 2014.
 Schmidt, Z. and Doty, D.R (1989): "System Analysis for Sucker-Rod Pumping."
SPE Production Engineering (May), p. 125. Richardson , TX : Society of
Petroleum Engineers.
 Zaba, J., (1968), Modern Oil Well Pumping. Tulsa, OK: PennWell Publishing Co.
 http://www.mpgpetrole**.com/fundamentals.html
 www.drill-pi*es.com
 www.drillingcontractor.org
 www.drillingsoft*are.com
 https://www.s*b.com/resources.aspx

ABOUT THE WRITER
Having more than 10 years of work experiences in Oil and
Gas Industry both exploration and development such as
Bandarjaya / Lampung III Project (at PT. Harpindo Mitra
Kharisama), Reevaluation of Diski Oil field - North Sumatra
basin (at TAC PEP – PKDP), and Preliminary Fractured
evaluation some oil fields (at PT. OPAC Barata-Kejora Gas
Bumi Mandiri), Evaluation for Klamono Block - Salawati Basin and Evaluation for Tebat
Agung Block - South Sumatera Basin (at Trada Petroleum Pte. Ltd.), Operation of
Kampung Minyak oilfield (at KSO Pertamina EP – PKM) and Formation Evaluation of
Tsimororo Field - Madagascar (at Lemigas), J1J3 Oil Fields - NW Java basin (at ECC).
He Was Graduated from Institute Technology of Bandung, Geology Engineering
Department in 2006 as S.T. (Sarjana Teknik) or Bachelor degree in Geology. Before that
He was graduated from SMUN 2 Cimahi (Senior High School) in 1998-2001, and from
SLTPN 9 Cimahi (Junior High School) in 1995-1998, also graduated SDN KIHAPIT I
(Elementary school) 1995.

Petroleum well completion overview

Petroleum well completion overview

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Petroleum well completion overview